Orthodontic treatments involve repositioning misaligned teeth and improving bite arrangements for improved cosmetic appearance and dental function. Conventionally, repositioning of teeth has been accomplished by what are commonly referred to as “braces.” Braces comprise a variety of elements such as brackets, bands, archwires, ligatures, and O-rings. After some of these elements are bonded to the teeth, periodic appointments with the treating doctor are required to adjust the braces. This involves bending or installing different archwires having different force-inducing properties, and/or replacing ligatures and O-rings.
An alternative to braces includes the use of elastic positioning dental appliances (also known as “aligners”) for repositioning teeth. Such an appliance can be comprised of a thin shell of elastic material that generally conforms to a patient's teeth but each appliance to be used at a treatment stage has a cavity geometry that is slightly out of alignment with the teeth arrangement at the start of that treatment stage. Placement of the elastic positioning dental appliance over the teeth applies controlled forces in specific locations to gradually move the teeth into a new arrangement as defined by the cavity of the appliance. Repetition of this process moves the teeth through a series of intermediate arrangements to a final desired arrangement. Due to the limited space within the oral cavity and extensive movements that some teeth typically undergo as a part of treatment, the teeth will often be moved throughout the series of intermediate tooth arrangements to properly arrange the teeth. Thus, a single patient treated with elastic positioning dental appliance may experience from 2 to perhaps 50 or more aligner stages (with an average of 25-30 aligner stages per arch) before achieving the final desired teeth arrangement.
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